Manufacture of cartridge cases and the like



March 26, 1945- w. H. RAVEN ET AL MANUFACTURE OF CARTRIDGE CASES AND THE LI KE Filed June 25, 1945 Jim Patented Mar. 26, 1946 UNETED STATES PATENT OFFICE ll/iANUFACTURE OF CARTRIDGE CASES AND THE LIKE Application June23, 1943, Serial No. 491,879 In Great Britain November 17, 1942 3 Claims.

This invention relates to the manufacture of drawn metal containers such as cartridge cases in which the length is great in relationship to the diameter, and the thickness of the base is great in relationship to the thickness of the body walls.

Cartridge cases of the type in question are normally made of high grade brass and in one piece from a comparatively thick blank of small diameter, the thickness of which is substantially the same as the thickness of the base of the finished case. Commencing by drawing with thick Walls and base, such cup is successively drawn to retain the thick based cup and produce medium thickness walls, and is then ironed by progressively smaller dies and punches which, whilst retaining the thick base, produce, by plastic flow. the required thin walls whose depth is great in relationship to its diameter. The pressures involved in this process, even with a relatively ductile metal such as high grade brass are very high so that the die life is short, and the amount of wall thinning which takes place on each passage through the dies is necessarily small due to the need for keeping these pressures within reasonable limits. Annealing wh-ere necessary takes place between draws, or passes through the dies, and in some instances the length of the cup walls is adjusted after one operation by facing the open end to suit a following operation.

One object of this invention is to enable such relatively deep cases to be made from steel, bearing in mind that most of the methods applicable to manufacture from brass would be relatively impracticable for steel, if only because of reduced rate of production.

Another object of the invention is the manufacture of a cartridge case or like container which comprises a ferrous metal case and a ferrous metal body preformed with complementary fitting and locating surfaces and secured together by welding at such surfaces.

According to further features of the invention a non-ferrous fusible metal, preferably copper, may be used to produce the weld and the container may subsequently be subjected to drawing so as to stress the Weld and provide a test for the strength thereof. Preferably the body part is produced by drawing and the base by coining, and the parts are shaped and/or positioned so as to form an annular channel in which the welding metal is trapped or held before and during fusing. In one mode of carrying out the invention, the parts so formed and positioned are arranged and heated so that the jointing metal flows into the joint, when it is fused, the welded parts being preferably subsequently processed. In connection with cartridge cases the weld is preferably located away from what is known as the point of separation, that is the point where breakage usually occurs, if at all, as a result of explosion pressures.

In the accompanying drawing,

Figs. 1 to 5 show in various stages of produc tion a drawn steel body for a cartridge case made in accordance with one example of the invention.

Figs. 6 to 9 show a coined steel base in various stages of production for fitting to the body Fig. 5.

Fig. 10 shows the fitting together of the parts shown in Figs. 5 and 9 prior to welding.

Fig. 11 shows the finished cartridge case.

In the manufacture of the body shown in Figs. 1 to 5 of the drawing, a cup a is drawn from a circular steel blank, the diameter of which is chosen in accordance with the known rules for cup drawing, and the thickness of which is slightly greater than the thickness required in the finished wall. Figs. 1, 2 and 3 show the first draws, while Fig. 4 shows a further draw which also includes some degree of ironing to reduce the wall thickness and give the necessary tapering of this thickness. Annealing as required may be performed between these stages of drawing, but is usually necessary only after the initial blank and draw as shown in Fig. 1. By appropriate selection of the original blank diameter, trimming to length may be rendered unnecessary during these stages. The bottom b of the resulting cup is now removed, preferably by piercing. leaving the tubular body 0 as shown in Fig. 5.

The base is made from the steel blank (1 shown in Fig. 6. The steel should be of a quality suitable for cold-working, and the blank is coined and re-coined in suitable tools and stages to give the forms d and (1 shown in Figs. 7' and 8 respectively. The baseis then machined to the form 2 shown in Fig. 9. Alternatively, the base can be machined from steel bar. In its finished form the base is a press fit in the end of the body.

The body 0 and base e are then assembled as shown in the Fig. 10, with a thin copper ring in position as shown which will ultimately form the weld. The assembly is then passed through a conveyor-type furnace, or other suitable furnace, at a temperature high enough to fuse the copper ring and efiect the welding together of the two parts. The assembly passes through the furnace in an inverted position with the open end downwards, the copper being thus able to ing the case after the annealing which takes place during the welding operation. The degree of hardness so obtained is dependent upon the amount of ironing which takes place duringthis operation. Drawing, after .welding, is also performed in such manner that pressure in one direction is applied direct to the base so asto stress the copper Weld and this provides a safeguard as a test of the strength ofthe weld.

The case is now in a condition and formsimi-lar to an advanced stage in the manufacture ofthe orthodox brass case, and the subsequent operations of tapering, necking, trimming the mouth and machining the head may'now follow normal procedure to complete the case as shown in Fig. 11.

The line a:-a: in Fig. 11 shows'the approximate location of the point of separation and it will be seen that the weld is located away from this point.

Thesteel cartridge case will,. of course, require a weather-proof finish, and for reasons connected with the gun itself, this finish must be metallic. This may take the form'of electrically deposited chromium or other metal preferably over a subcoating such as nickel.

This feature of chromium platingis applicable to cartridge casesof any suitablematerial and construction other than as above described. Chromium is selected as having an important characteristic in that the hard chromium skin reduces theefiort of-inserting the case. into and (especially after firing) of'the-eifort of extracting the case fro-m the breechlofa .gun. In Consequence the strainon-the :gun mechanism and the risk of .fraction of the cartridge rcase during extraction aremuchreduceiiall of which results of selecting chromium are in excess :of the normally known effects of providing a hard protective coating.

The invention is obviously-not limited :tov all the details of construction ofthe example above ,described, many of which will becapable of modification without departing from the :nature of "the invention.

:For example-the body partcould bemadefrom solid drawn tube instead of by blanking and drawin as herein describedand the shaping-produced by swaging or othermanipulation, or such body could be made from welded tube or other wise with a longitudinal weld, thoughtherewould obviously be prejudice against having such a joint. Fig. 5 may be taken to represent such a tube prepared for receiving a .base.

circular base part having a pre-formed circumferential groove in the location of an extractor groove, placing anon-ferrous metal ring in said circumferential groove, said ring having a lower jfusion pointthanthe said body part and base part, placing the body part on the base so that the end of said body part overlies .said groove and enclosessaid non-ferrous metal ring, heating the assembled body and base parts in inverted position whereby the non-ferrous ring is heated to fusion and flows betweenand unites the adjacent surfaces, and forming an extractor groove around said base partxbymachining away at least that part of the body which overlies said pre-formed groove.

.2. A method of making a cartridge case comprising; forming atubular ferrous body part, forming a circular ferrous base part having a preformed circumferential groove in the location of anextractor groove, placing a non-ferrous metal .ring in saidcircumferential groove, said ring having a lower fusionpcint than the said body part and base part, placing the body part on the base so that the end of said body part overlies said groove and encloses said non-ferrous metal ring.

heating the assembled body and base parts in inverted position whereby the non-ferrous ring is heated .to fusion and flows between and unites the adjacent surfaces, and forming an extractor groove-around. said base part by machining away at .least that part of the body which overlies said pre-formed groove.

3..A method of making a cartridge case comprising; forming a tubular steelbody part, forming .by operations including an initial coining operation, a circular steel base part having a preformed circumferential groovein the location of an extractor groove, placing a copper ring in said circumferential groove, said ring having a lower fusion point than the said body part and base part, placing the body part on the base So that r the end of said body part overlies said groove and encloses said copper ring, heating the assembled body-and base parts in inverted position whereby the copper ring is heatedto fusion andflows between and unites the adjacent surfaces, and forming an extractor groove around said base part by machining away at least that part of the body whichoverlies said pre-formed groove.

W. H. RAVEN.

W. H. HERON. 

